1. Field of the Invention
The invention relates to a plasma display panel (PDP) used as a planar display for a television set and a computer, a method of driving the same, a circuit for driving the same, and a display unit including the same. More particularly, the invention relates to an alternating current (AC) memory operation type plasma display panel, a method of driving the same, a circuit for driving the same, and a display unit including the same.
2. Description of the Related Art
A plasma display panel has many advantages that it can be fabricated thin, it can display images without flickers, it presents a high display contrast, it can be fabricated in a relatively large display screen, it has a high response speed, it presents superior visibility because it emits lights, and it can display color images by means of three phosphors for converting ultra-violet rays into visible lights of three primary colors, that is, red, green and blue. Hence, a plasma display panel is used as a display unit in a computer, a work station, a television set, and so on.
A plasma display panel is grouped into an alternating current (AC) type one in which electrodes covered with dielectric material are operated indirectly in AC discharge condition, and a direct current (DC) type one in which electrodes are exposed to a discharge space, and operated in DC discharge condition. An alternating current type plasma display panel is further grouped into a memory operation type one which makes use of a memory function by which sustaining discharge is continued in a cell, and a refresh operation type one which makes no use of the above-mentioned memory function. Herein, a cell means a minimum unit for constituting a display screen. A display screen is comprised of a plurality of cells arranged in a matrix.
In a plasma display panel, a luminance of each of colors displayed in each of cells is in proportion to the number of sustaining pulses. Since the above-mentioned refresh operation type plasma display panel makes no use of the memory function, if a display capacity is increased, a luminance would be reduced. Accordingly, when images are displayed with a high luminance and in a large capacity, a memory operation type plasma display panel is predominantly used.
FIG. 1 is a partial perspective view of a structure of a conventional alternating current (AC) memory operation type plasma display panel 1, and FIG. 2 is an upper view of the conventional plasma display panel 1 with a later mentioned front insulating substrate 2 being removed.
A conventional plasma display panel 1 such as one illustrated in FIGS. 1 and 2 is suggested, for instance, in Japanese Patent No. 3036496 (Japanese Patent Application Publication No. 11-161226) or Japanese Patent Application Publication No. 11-202831. FIG. 2 is an upper view obtained when the conventional plasma display panel 1 illustrated in FIG. 1 is rotated by 90 degrees.
The conventional plasma display panel 1 includes a front insulating substrate 2 and a rear insulating substrate 10. As illustrated in FIGS. 1 and 2, a plurality of stripe-shaped scanning electrodes 3 and a plurality of stripe-shaped sustaining electrodes 4 are alternately arranged in a row direction (an up to down direction in FIG. 1) on a lower surface of the front insulating substrate 2. Both of the scanning electrodes 3 and the sustaining electrodes 4 extend in a column direction (a left to right direction in FIG. 1). Each of the scanning electrodes 3 is spaced away from the adjacent sustaining electrodes 4 by a discharge gap 5. The front insulating substrate 2 is composed, for instance, of soda-lime glass, similarly to the rear insulating substrate 10. The scanning electrodes 3 and the sustaining electrodes 4 are comprised of an electrically conductive transparent thin film composed, for instance, of tin oxide, indium oxide or indium tin oxide (ITO).
A first trace electrode 6 extends in the column direction along an edge of and on a lower surface of each of the scanning electrodes 3. Similarly, a second trace electrode 7 extends in the column direction along an edge of and on a lower surface of each of the sustaining electrodes 4. The first and second trace electrodes 6 and 7 are comprised of a metal film such as a thick silver film or a thin aluminum or copper film. The first and second trace electrodes 6 and 7 reduce electrical resistance between the scanning and sustaining electrodes 3 and 4 both having a low electrical conductivity, and a later mentioned driver circuit electrically connected to the scanning and sustaining electrodes 3 and 4.
A lower surface of the front insulating substrate 2, the scanning electrodes 3, the sustaining electrodes 4, the first trace electrodes 6 and the second trace electrodes 7 are covered with a transparent dielectric layer 8. The transparent dielectric layer 8 is composed of glass having a low melting point, for instance.
The transparent dielectric layer 8 is covered with a protection layer 9 which protects the dielectric layer 8 from ion bombardment in discharge. The protection layer 9 is composed of a material having a high secondary electron emission coefficient and a high resistance to sputtering, such as magnesium oxide.
On an upper surface of the rear insulating substrate 10 is formed a plurality of stripe-shaped data electrodes 11 equally spaced away from one another and extending in the row direction, that is, a direction perpendicular to a direction in -which the scanning electrodes 3 and the sustaining electrodes 4 extend. The data electrodes 11 are comprised of a silver film, for instance.
The data electrodes 11 and an upper surface of the rear insulating substrate 10 are covered with a white dielectric layer 12.
On an upper surface of the dielectric layer 12 is formed a plurality of stripe-shaped partition walls 13 extending in the row direction. When viewed from an upper side, the partition walls 13 are arranged between the adjacent data electrodes 11. The partition walls 13 partition a cell.
Three phosphor layers 14R, 14G and 14B are formed on an upper surface of the dielectric layer 12 and sidewalls of the partition walls 13. The three phosphor layers 14R, 14G and 14B convert ultra-violet rays produced by gas discharge, into three visible lights of three primary colors, that is, red (R), green (G) and blue (B). The phosphor layers 14R, 14G and 14B are arranged in the column direction repeatedly in this order. Each of the three phosphor layers 14R, 14G and 14B extends in the raw direction.
Each of spaces surrounded by a lower surface of the protection layer 9, each of surfaces of the phosphor layers 14R, 14G and 14B, and sidewalls of the adjacent partition walls 13 defines a discharge gas space 15. The discharge gas space 15 is filled with discharge gas comprised of xenon (Xe), helium (He) or neon (Ne) alone or in combination at a predetermined pressure. A region surrounded by the scanning electrodes 3, the sustaining electrodes 4, the first trace electrode 6, the second trace electrode 7, the data electrodes 11, the phosphor layer 14R, 14G or 14B, and the discharge gas space 15 defines a cell.
FIG. 3 is a block diagram of the conventional plasma display panel 1 illustrated in FIG. 1, and a conventional driver circuit for driving the plasma display panel 1.
The plasma display panel 1 illustrated in FIG. 3 includes N scanning electrodes 31 to 3N equally spaced away from one another and extending in the column direction wherein N is an integer equal to or greater than one (1), N sustaining electrodes 41 to 4N equally spaced away from one another and extending in the column direction, and M data electrodes 111 to 11M equally spaced away from one another and extending in the row direction wherein M is an integer equal to or greater than one (1). Accordingly, the plasma display panel 1 includes (Nxc3x97M) cells.
The driver circuit is comprised of an image processor 21, a drive controller 22, a sustaining electrode driver 23, a scanning electrode driver 24, and a data driver 25.
The image processor 21 receives an analog image signal Sp transmitted from an external circuit (not illustrated), and applies analog-digital conversion to the analog image signal Sp to thereby produce digital image data Dp for driving the plasma display panel 1. The image processor 21 further produces data Ds indicative of the number of sustaining pulses which determines a luminance of each of colors displayed in each of the cells in the plasma display panel 1.
The drive controller 22 produces a sustaining electrode driver control signal SSU for controlling the sustaining electrode driver 23, scanning electrode driver control signals SSC1 to SSC4 for controlling the scanning electrode driver 24, and a data driver control signal SDD for controlling the data driver 25, based on the digital image data Dp and the data Ds both received from the image processor 21.
The sustaining electrode driver 23 is comprised of a sustaining driver 26 electrically connected at one end thereof to the sustaining electrodes 41 to 4N.
The sustaining driver 26 produces a sustaining pulse PSU having a predetermined waveform, based on the sustaining electrode driver control signal SSU received from the drive controller 22, and applies the sustaining pulse PSU to the sustaining electrodes 41 to 4N.
The scanning electrode driver 24 is comprised of a scanning base driver 27, a sustaining driver 28, an erasion driver 29, a priming driver 30, and a scanning pulse driver 31.
The scanning base driver 27 produces scanning base pulses, based on the scanning electrode driver control signals SSC1 transmitted from the drive controller 22.
The sustaining driver 28 produces sustaining pulses, based on the scanning electrode driver control signals SSC2 transmitted from the drive controller 22.
The erasion driver 29 produces erasion pulses, based on the scanning electrode driver control signals SSC3 transmitted from the drive controller 22.
The priming driver 30 produces priming pulses, based on the scanning electrode driver control signals SSC4 transmitted from the drive controller 22.
The scanning pulse driver 31 produces scanning pulses PSC1 to PSCN each having a predetermined waveform, based on the scanning base pulses transmitted from the scanning base driver 27, the sustaining pulses transmitted from the sustaining driver 28, the erasion pulses transmitted from the erasion driver 29, and the priming pulses transmitted from the priming driver 30, and applies the thus produced scanning pulses PSC1 to PSCN to the scanning electrodes 31 to 3N, respectively.
The data driver 25 produces data pulses having different waveforms from one another, based on the data driver control signal SDD transmitted from the drive controller 22, and applies the thus produced data pulses to the data electrodes 111 to 11M.
FIG. 4 is a block diagram of the image processor 21.
The image processor 21 operates in accordance with a peak luminance enhancement (PLE) process in which a luminance level of a display screen is controlled in accordance with an average peak luminance (APL) level of the image signal Sp to thereby suppress an increase in power consumption and accomplish a high peak luminance.
The image processor 21 is comprised of a first circuit 32 for processing image signals, a second circuit 33 for carrying out operation, a third circuit 34 for controlling the number of sustaining pulses, and a fourth circuit 35 for controlling a sub-field.
Hereinbelow is explained a sub-field.
In the plasma display panel 1, a luminance of each of colors displayed in each of the cells is in proportion to the number of sustaining pulses, as mentioned earlier. Images are displayed in gray scales by changing the number of sustaining pulses in one frame period in which frames constituting one display screen are displayed. Hence, a frame is comprised of a plurality of sub-fields, and a binary image is displayed in each of sub-fields. Further, a period of time in which a light is emitted in each of the cells is weighed in each of sub-fields. Such a process as mentioned above is called a sub-field process.
For instance, if a frame is comprised of eight sub-fields, and a ratio in the number of sustaining pulses in each of sub-fields is determined as 1:2:4:8:16:32:64:128, an image can be displayed in 256 (28=256) gray scales.
The first circuit 32 receives an analog image signal Sp from an external circuit (not illustrated), and converts the received analog image signal Sp into digital image data. Then, the first circuit 32 applies reverse-gamma compensation to the digital image data, and transmits the resultant image data DP1, to both the second circuit 33 and the fourth circuit 35.
Herein, reverse-gamma compensation indicates the following compensation. The image signal Sp transmitted from an external circuit has characteristics which have been gamma-compensated to match with gamma characteristics of a cathode ray tube (CRT) display. The reverse-gamma compensation is carried out in order to cause characteristics of the above-mentioned digital image data to match with linear gamma characteristics of the plasma display panel 1.
The second circuit 33 computes an average peak luminance level over a display screen per a frame, and transmits computation results CR to the third circuit 34.
The third circuit 34 produces the total number SS of sustaining pulses per a frame in association with the average peak luminance level, and data Ds indicative of the number of sustaining pulses in each of the sub-fields, based on the computation results CR transmitted from the second circuit 33.
The fourth circuit 35 produces digital image data Dp in accordance with which the plasma display panel 1 is driven, based on the image data DP1, in accordance with the total number SS of sustaining pulses. The fourth circuit 35 then transmits the thus produced digital image data Dp to the drive controller 22 together with the data Ds indicative of the number of sustaining pulses in each of the sub-fields.
FIG. 5 is a timing chart of an operation of the above-mentioned driver circuit. Hereinbelow is explained an operation of the plasma display panel 1 with reference to FIG. 5.
FIG. 5 illustrates waveforms of signals in a certain sub-field SF of a frame. FIG. 5(A) shows an example of a scanning pulse Psck to be applied to the scanning electrode 3k wherein xe2x80x9ckxe2x80x9d is an integer equal to or greater than one (1), but equal to or smaller than N (1xe2x89xa6kxe2x89xa6N), FIG. 5(B) shows an example of a sustaining pulse Psu to be applied to the sustaining electrodes 41 to 4N, and FIG. 5(C) shows an example of a data pulse PDj to be applied to the data electrode 10j wherein xe2x80x9cjxe2x80x9d is an integer equal to or greater than one (1), but equal to or smaller than M (1xe2x89xa6jxe2x89xa6M).
A sub-field SF is comprised of a priming period Tp in which weak discharge is generated for reducing wall charges attracted to the scanning electrodes 31 to 3N and the sustaining electrodes 41 to 4N by priming period, an address period TA in which a cell in which an image is displayed is selected, a sustaining period Ts in which a light is emitted in the selected cell, and a charge-erasion period TE in which wall charges attracted to the scanning electrodes 31 to 3N and the sustaining electrodes 41 to 4N in the sustaining period Ts in the selected cell are erased.
The first circuit 32 receives an analog image signal Sp from an external circuit (not illustrated), and converts the received analog image signal Sp into digital image data. The first circuit 32 further applies reverse-gamma compensation to the digital image data, and transmits the resultant image data DP1 to the second circuit 33 and the fourth circuit 35.
On receipt of the image data DP1, the second circuit 33 computes an average peak luminance level over a display plane per a frame, and transmits the computation results CR to the third circuit 34. The third circuit 34 produces the total number SS of sustaining pulses per a frame in accordance with the average peak luminance level, and data Ds indicative of the number of sustaining pulses in each of the sub-fields, based on the computation results CR transmitted from the second circuit 33. The third circuit 34 produces the data Ds such that the number of sustaining pulses is increased for raising a luminance level over a display plane, if the average peak luminance level is relatively low, and the number of sustaining pulses is reduced for lowering a luminance level over a display plane, if the average peak luminance level is relatively high.
The fourth circuit 35 produces digital image data Dp in accordance with which the plasma display panel 1 is driven, based on the image data DP1, in accordance with the total number SS of sustaining pulses. The fourth circuit 35 then transmits the thus produced digital image data Dp to the drive controller 22 together with the data Ds indicative of the number of sustaining pulses in each of the sub-fields.
The drive controller 22 produces a sustaining electrode driver control signal SSU for controlling the sustaining electrode driver 23, scanning electrode driver control signals SSC1 to SSC4 for controlling the scanning electrode driver 24, and a data driver control signal SDD for controlling the data driver 25, based on the digital image data Dp and the data Ds both received from the image processor 21.
As a result, in the priming period Tp, a serration-shaped and positive priming pulse PPRP illustrated in FIG. 5(A) is applied to the scanning electrodes 31 to 3N, and a negative priming pulse PPRN illustrated in FIG. 5(B) is applied to the sustaining electrodes 41 to 4N. Herein, a positive pulse means a pulse having a voltage higher than a sustaining voltage Vs, and a negative pulse means a pulse having a voltage smaller than the sustaining voltage Vs. Thus, priming discharge is generated in the discharge gas space 15 close to the discharge gap 5 formed between each of the scanning electrode 31 to 3N and each of the sustaining electrode 41 to 4N. The priming discharge produces active particles which will assist in generation of sustaining discharge in a cell. In addition, negative wall charges are accumulated on the scanning electrodes 31 to 3N, and positive wall charges are accumulated on the sustaining electrodes 41 to 4N.
Then, as illustrated in FIG. 5(B), after voltages of the sustaining electrode 41 to 4N are sustained at the sustaining voltage Vs, a first charge-erasing pulse PEEN1 which is negative and serration-shaped, illustrated in FIG. 5(A) is applied to the scanning electrode 31 to 3N. As a result, weak discharge is generated in all of the cells, and accordingly, the negative wall charges attracted on the scanning electrode 31 to 3N and the positive wall charges attracted on the sustaining electrodes 41 to 4N are reduced.
In the address period TA, a cell or cells in which a light is emitted is selected among the plurality of cells. All of the sustaining electrodes 41 to 4N are sustained at the sustaining voltage Vs, as illustrated in FIG. 5(B), and a negative standard pulse PWBN is applied to the scanning electrode 31 to 3N as a standard voltage, as illustrated in FIG. 5(A).
In such a condition as mentioned above, in order to select a cell or cells in each of columns, a negative scanning pulse PWSN illustrated in FIG, 5(A) is applied to the scanning electrode in a selected column. In addition, a positive data pulse PDT illustrated in FIG. 5(C) is applied to a data electrode in an associated row. For instance, the negative scanning pulse PWSN is applied to the scanning electrode 3k, and the positive data pulse PDT is applied to the data electrode 11j. 
The data pulse PDT is a pulse for selecting a cell in which an image is to be displayed. In a cell located at an intersection of the scanning electrode 3k to which the negative scanning pulse PWSN was applied and the data electrode 11j to which the positive data pulse PDT was applied, there are generated facing discharge, and area discharge triggered by the facing discharge as selecting or writing discharge between the scanning electrode 3k and the sustaining electrode 4k. 
In a cell in which the selecting or writing discharge was generated, positive wall charges are accumulated on the scanning electrodes 31 to 3N, and negative wall charges are accumulated on the sustaining electrodes 41 to 4N. In contrast, in a cell in which the selecting or writing discharge is no generated, only wall charges remaining after removal of wall charges by the negative first charge-erasing pulse PEEN1 are accumulated on the scanning electrodes 31 to 3N and the sustaining electrodes 41 to 4N. Hence, an amount of wall charges in a cell the selecting or writing discharge is no generated is quite smaller than an amount of wall charges in which the selecting or writing discharge was generated.
In the sustaining period Ts, a light is emitted in a selected cell. A negative sustaining pulse PSUN2 illustrated in FIG. 5(B) is applied to all of the sustaining electrodes 41 to 4N a plurality of times, and at the same time, a negative sustaining pulse PSUN1 illustrated in FIG. 5(A) is applied to the scanning electrodes 31 to 3N a plurality of times. Since wall charges are accumulated on the scanning electrodes 31 to SN and the sustaining electrodes 41 to 4N in a small amount in a cell which was not selected in the address period TA, there is not generated sustaining charge caused by a combination of a voltage of the negative sustaining pulse PSUN1 or PSUN2 and a wall charge voltage, and hence, a cell does not emit a light.
In contrast, since positive wall charges are accumulated on the scanning electrodes 31 to 3N and negative wall charges are accumulated on the sustaining electrodes 41 to 4N in a cell having been selected in the address period TA, a voltage of the negative sustaining pulse PSUN1 or PSUN2 and a wall charge voltage are combined to each other, and hence, a voltage between the scanning electrodes 31 to 3N and the sustaining electrodes 41 to 4N exceeds a critical voltage at which a discharge starts. As a result, there is generated sustaining discharge, and hence, a cell emits a light.
As is obvious in view of FIG. 5(A) and 5(B), a pulse width of the negative sustaining pulse PSUN1 or PSUN2 to be first applied to the scanning or sustaining electrodes is set wider than a pulse width of the following negative sustaining pulses PSUN1 and PSUN2. This is for the purpose that a cell having been selected in the address period TA can surely emit a light, as suggested in Japanese Patent No. 2674485 (Japanese Patent Application Publication No. 7-134565).
As a result of generation of sustaining discharge by the first applied negative sustaining pulses PSUN1 and PSUN2, wall charges are rearranged such that voltages applied to the scanning electrodes 31 to 3N and the sustaining electrodes 41 to 4N are cancelled. Accordingly, positive charges are accumulated on the sustaining electrodes 41 to 4N, and negative charges are accumulated on the scanning electrodes 31 to 3N. Since a negative sustaining pulse PSUN1 is next applied to the scanning electrodes 31 to 3N, an effective voltage to be applied to the discharge gas space 15 by combination of a voltage of wall charges and a voltage of the negative sustaining pulse PSUN1 exceeds a critical voltage at which a discharge starts, resulting in that sustaining discharge is generated again.
Thereafter, the same steps as mentioned above are alternately repeated, and resultingly, sustaining discharge is repeatedly generated. A luminance in each of colors displayed in each of cells is defined by the number of repetition of the sustaining discharge.
In the charge-erasion period TE, a negative and serration-shaped, second charge-erasion pulse PEEN2 illustrated in FIG. 5(A) is applied to the scanning electrodes 31 to 3N. Accordingly, there is generated weak discharge in all of the cells during a slope of the negative and serration-shaped, second charge-erasion pulse PEEN2, resulting in that negative wall charges accumulated on the scanning electrodes 31 to 3N and positive wall charges accumulated on the sustaining electrodes 41 to 4N in a cell emitting a light in the sustaining period Ts, and hence, a charge condition in all of the cells in the plasma display panel 1 are uniformized.
In the above-mentioned conventional driver circuit for driving the plasma display panel 1, an image is displayed at a certain gray scale by changing the number of sustaining pulses in one frame period, and hence, it is not possible to display an image at a gray scale greater than the number of sustaining pulses.
As a method of reducing power consumption in a plasma display panel, there have been conventionally suggested a method (hereinafter, referred to as xe2x80x9cfirst methodxe2x80x9d) of reducing the number of sustaining pulses to be applied to the sustaining electrodes 41 to 4N in one frame period, and a method (hereinafter, referred to as xe2x80x9csecond methodxe2x80x9d) of lowering the sustaining voltage Vs t thereby reduce a light intensity per one sustaining pulse.
However, the first method is accompanied with a problem that if the total number of sustaining pulses to be applied to the sustaining electrodes 41 to 4N in one frame period is smaller than 255, it would not be possible to display an image at 256 gray scales.
The second method is accompanied with a problem that if the conventional plasma display panel 1 operates in accordance with the second method, a luminance in each of cells varies in different degrees when the sustaining voltage Vs is reduced, resulting in that it would be quite difficult to display images at a uniform gray scale. The reason is as follows.
FIG. 6 is a graph showing an example of a relation between a luminance and a sustaining voltage in a cell in a conventional plasma display panel.
Some of conventional plasma display panels include cells each having a relation between a luminance and a sustaining voltage which relation is different from others, as shown with curves A and B in FIG. 6. This is caused by variance in fabrication of a plasma display panel, such as a thickness of the dielectric layer 9 formed on a lower surface of the front insulating substrate 2, or a discharge gap between the scanning electrodes 31 to 3N and the sustaining electrodes 41 to 4N.
Hence, a difference in a luminance in cells was reduced in a conventional plasma display panel by selecting a sustaining voltage VS1 close to a voltage at which a luminance is saturated. Accordingly, if the sustaining Vs is made smaller than the sustaining voltage VS1 in accordance with the above-mentioned second method in order to reduce power consumption, a plasma display panel is operated with a sustaining voltage Vs involved in an area VAR (see FIG. 6) in which cells have different relations between a luminance and a sustaining voltage from one another. As a result, a luminance in the cells varies in different degrees, and hence, it would be quite difficult to display images at a uniform gray scale.
Furthermore, if the number of cells emitting a light in a plasma display panel, an impedance in the driver circuit would be changed accordingly, resulting in that a luminance in a cell is likely to be varied.
In order to solve the above-mentioned problems, Japanese Patent Application Publication No. 5-135701 has suggested a plasma display panel in which a cell is comprised of a sustaining electrode, and a plurality of scanning electrodes each spaced away form the sustaining electrode by a predetermined length. By selecting one or more of scanning electrodes among the scanning electrodes, an area in which sustaining discharged is generated is controlled for varying a display area, to thereby vary a luminance of a cell and power consumption.
However, the suggested plasma display panel is accompanied with the following problems.
First, it is necessary in the suggested plasma display panel to arrange scanning electrodes below a front insulating substrate in the number equal to or greater than the number of scanning lines, resulting in an increase in a size of a plasma display panel relative to the number of scanning lines.
Second, the suggested plasma display panel includes a plurality of scanning electrodes per a cell. It would be necessary in the suggested plasma display panel to arrange an opaque trace electrode under each of the scanning electrodes for shielding a light. This results in reduction in an aperture ratio. Consequently, a luminance is lowered, and hence, it would be quite difficult to accomplish a high luminance.
Third, it would be necessary for the suggested plasma display panel to include circuits for driving such a plurality of scanning electrodes, resulting in an increase in complexity and fabrication costs of the plasma display panel.
Japanese Patent Application Publication No. 2000-113827 has suggested a plasma display panel comprised of a first glass substrate, a first electrode formed on a surface of the first glass substrate, a second electrode formed on a surface of the first glass substrate such that the second electrode is spaced away from the first electrode by a predetermined distance, a dielectric layer formed on a surface of the first glass substrate so as to cover the first and second electrodes therewith, a second glass substrate facing the first glass substrate, a plurality of partition walls arranged between the first and second glass substrates so as to define a discharge space above the first and second electrodes, a phosphor layer formed on the second glass substrate so that the phosphor layer faces the discharge space, and a gas filled in the discharge space and producing ultra-violet lights for exciting the phosphor layer, characterized in that the dielectric layer has a thickness varying in association with portions of the first electrode, and further in association with portions of the second electrode.
Japanese Patent Application Publication No. 2000-156167 has suggested an alternating current (AC) memory operation type plasma display panel including electrodes facing each other with a discharge gap sandwiched therebetween, which electrodes are designed to have a plurality of small apertures.
Japanese Patent Application Publication No. 9-330665 has suggested an alternating current (AC) memory operation type plasma display panel including a pair of sustaining electrodes buried in a dielectric layer in a depth shallower towards a discharge gap from edges of the sustaining electrodes located opposite to the discharge gap.
Japanese Patent Application Publication No. 2000-294149 has suggested a plasma display unit comprised of a first substrate, a second substrate, a first dielectric layer formed on the first substrate, first and second electrodes both formed on the first substrate and covered with the dielectric layer, and producing plasma through the dielectric layer in a plurality of discharge cells, and a plurality of partition walls formed on the second substrate. Each of the first and second electrodes is comprised of an inner electrode located in the vicinity of a discharge gap, an outer electrode spaced away from the inner electrode, and a connector electrode for electrically connecting the inner and outer electrodes to each other. Orthogonal projection in an area in which the connector electrode does not overlap the partition walls, viewed from a direction which passes the first and second substrates is not continuous over both of the outer and inner electrodes.
Japanese Patent Application Publication No. 2000-195431 has suggested a plasma display panel including a grid-shaped partition wall arranged between front and rear substrates, and comprised of first portions extending in a row direction and second portions extending in a column direction, and a raised portion projecting towards the second portions to thereby eliminate a space between itself and the second portions.
Japanese Patent Application Publications Nos. 2000-267627 and 2000-214822 have suggested a method of driving a plasma display panel which method is capable of enhancing a contrast and reducing power consumption.
However, the above-mentioned problems remain unsolved even in the above-listed Japanese Patent Application Publications.
In view of the above-mentioned problems in the conventional plasma display panels, it is an object of the present invention to provide a plasma display panel which is capable of being fabricated in a smaller size, more readily and in smaller fabrication costs, displaying images at a gray scale equal to or greater than the number of sustaining pulses, and reducing power consumption with a high and uniform gray scale being maintained.
It is also an object of the present invention to provide a method of driving a plasma display panel which method is capable of doing the same.
It is further an object of the present invention to provide a circuit for driving a plasma display panel which circuit is capable of doing the same.
It is further an object of the present invention to provide a plasma display unit which is capable of doing the same.
In one aspect of the present invention, there is provided a plasma display panel including a plurality of cells arranged in a matrix, wherein each of the cells includes (a) a scanning electrode having partial cutout, (b) a sustaining electrode having partial cutout, spaced away from the scanning electrode by a discharge gap in mirror-symmetry with a centerline of the discharge gap extending in a first direction, (c) a first trace electrode extending in the first direction on the opposite side of the scanning electrode about the discharge gap such that the first trace electrode makes electrical contact with the scanning electrode and further with a scanning electrode of an adjacent cell, and (d) a second trace electrode extending in the first direction on the opposite side of the sustaining electrode about the discharge gap such that the second trace electrode makes electrical contact with the sustaining electrode and further with a sustaining electrode of an adjacent cell.
For instance, the partial cutout defines an area of the cell in which sustaining discharge is most intensive.
For instance, the scanning electrode may be comprised of a single first part facing the discharge gap and extending in the first direction, and two second parts extending in a second direction perpendicular to the first direction, and spaced away from each other in parallel, wherein the first part is connected at its opposite ends to the second parts, and each of the second parts makes electrical contact with the first trace electrode.
For instance, each of the second parts makes electrical contact at distal ends thereof with the first trace electrode.
For instance, the sustaining electrode may be comprised of a single first part facing the discharge gap and extending in the first direction, and two second parts extending in a second direction perpendicular to the first direction, and spaced away from each other in parallel, wherein the first part is connected at its opposite ends to the second parts, and each of the second parts makes electrical contact with the second trace electrode.
For instance, each of the second parts makes electrical contact at distal ends thereof with the second trace electrode.
For instance, the scanning electrode may be comprised of a plurality of first parts extending in the first direction, and two second parts extending in a second direction perpendicular to the first direction, and spaced away from each other in parallel, wherein the first part is connected at its opposite ends to the second parts, one of the first parts faces the discharge gap, and the rest of the first parts are spaced away from one another at the opposite side of the one of the first parts about the discharge gap, and each of the second parts makes electrical contact with the first trace electrode.
For instance, the first parts may be equal in width to one another.
For instance, the first parts may be equally spaced away from one another.
For instance, one of the first parts is located on the first trace electrode in electrical contact.
For instance, the sustaining electrode is comprised of a plurality of first parts extending in the first direction, and two second parts extending in a second direction perpendicular to the first direction; and spaced away from each other in parallel, wherein each of the first parts is connected at its opposite ends to the second parts, one of the first parts faces the discharge gap, and the rest of the first parts are spaced away from one another at the opposite side of the one of the first parts about the discharge gap, and each of the second parts makes electrical contact with the second trace electrode.
For instance, the scanning electrode, the sustaining electrode, and the first and second trace electrodes are formed on an electrically insulating substrate, and the plasma display panel may further include a dielectric layer formed on the electrically insulating substrate, covering the scanning electrode, the sustaining electrode, and the first and second trace electrodes therewith, the dielectric layer being comprised of a first portion covering therewith an area including the discharge gap, and a second portion other than the first portion, the first portion having a thickness smaller than a thickness of the second portion.
For instance, the scanning electrode, the sustaining electrode, and the first and second trace electrodes are formed on an electrically insulating substrate, and the plasma display panel may further include a dielectric layer formed on the electrically insulating substrate, covering the scanning electrode, the sustaining electrode, and the first and second trace electrodes therewith, the dielectric layer being comprised of a first portion covering therewith an area including the discharge gap, and a second portion other than the first portion, the first portion having a dielectric constant higher than the same of the second portion.
For instance, each of the scanning and sustaining electrodes is comprised of a electrically conductive transparent thin film, and each of the first and second trace electrodes is comprised of a metal film.
There is further provided a plasma display panel including a plurality of cells arranged in a matrix, wherein each of the cells includes (a) a first scanning electrode extending in a first direction, (b) a first sustaining electrode spaced away from the first scanning electrode by a discharge gap, and extending in the first direction, (c) at least one second scanning electrode spaced away from the first scanning electrode at the opposite side of the first scanning electrode about the discharge gap, (d) at least one second sustaining electrode spaced away from the first sustaining electrode at the opposite side of the first sustaining electrode about the discharge gap, (e) a first trace electrode comprised of a single first part extending in the first direction, and two second parts extending in a second direction perpendicular to the first direction above partition walls extending in the direction for partitioning the cells, the first part and second parts being connected to each other above the partition walls, the first part being spaced away from a second scanning electrode remotest from the discharge gap among the at least one second scanning electrode, the first and second scanning electrodes making electrical contact with the second parts above the partition walls, and (f) a second trace electrode comprised of a single first part extending in the first direction, and two second parts extending in the second direction above the partition walls, the first part and second parts being connected to each other above the partition walls, the first part being spaced away from a second sustaining electrode remotest from the discharge gap among the at least one second sustaining electrode, the first and second sustaining electrodes making electrical contact with the second parts above the partition walls.
For instance, the plasma display panel may include a plurality of second scanning electrodes which are equal in width to one another.
For instance, the plasma display panel may include a plurality of second sustaining electrodes which are equal in width to one another.
For instance, each of the first and second scanning electrodes and each of the first and second sustaining electrodes may be comprised of a electrically conductive transparent thin film, and each of the first and second trace electrodes may be comprised of a metal film.
In another aspect of the present invention, there is provided a method of driving a plasma display panel defined above, including the step of changing the number of sustaining pulses to be applied to the scanning and sustaining electrodes in a sustaining period in at least one sub-field among a plurality of sub-fields constituting a frame, for displaying images in a gray scale, wherein a curve indicating a relation between a luminance and a sustaining voltage in the cell includes at least one intermediate region in which a luminance remains almost unchanged even if the sustaining voltage is increased, and the sustaining pulses have an amplitude equal to the sustaining voltage.
There is further provided a method of driving a plasma display panel defined above, including the step of changing the number of sustaining pulses to be applied to the scanning and sustaining electrodes in a sustaining period in at least one sub-field among a plurality of sub-fields constituting a frame, for displaying images in a gray scale, wherein a curve indicating a relation between a luminance and a sustaining voltage in the cell includes at least one intermediate region in which a luminance remains almost unchanged even if the sustaining voltage is increased, and one of the sustaining pulses has an amplitude equal to the sustaining voltage.
In still another aspect of the present invention, there is provided a circuit for driving a plasma display panel defined above by changing the number of sustaining-pulses to be applied to the scanning and sustaining electrodes in a sustaining period in at least one sub-field among a plurality of sub-fields constituting a frame, for displaying images in a gray scale, the circuit including (a) a first circuit for operating an average luminance level of image data per a frame, (b) a second circuit for transmitting, based on the results of operation having been carried out by the first circuit, data indicative the total number of sustaining pulses in the frame in accordance with the average luminance level, and data indicative of the number of sustaining pulses for each of sub-fields which number determines a luminance in each of the cells, (c) a third circuit for selecting, based on the results and the total number of sustaining pulses, one of an amplitude of a first sustaining voltage close to a voltage at which a luminance is saturated, and an amplitude of a certain period of second sustaining amplitude in which a luminance remains almost unchanged even if the sustaining voltage is increased, as an amplitude of a sustaining voltage in each of the sub-fields, and for transmitting an amplitude selection signal indicative of the thus selected amplitude, and (d) a fourth circuit for producing image data by which the plasma display panel is driven, based on the image data, in accordance with the amplitude selection signal, wherein an amplitude of the second sustaining voltage is selected as an amplitude of a sustaining pulse to be applied to the scanning and sustaining electrodes in a sustaining period in at least one sub-field among the plurality of sub-fields.
There is further provided a circuit for driving a plasma display panel defined in claim 1 by changing the number of sustaining pulses to be applied to the scanning and sustaining electrodes in a sustaining period in at least one sub-field among a plurality of sub-fields constituting a frame, for displaying images in a gray scale, the circuit including (a) a first circuit for operating an average luminance level of image data per a frame, (b) a second circuit for transmitting, based on the results of operation having been carried out by the first circuit, data indicative the total number of sustaining pulses in the frame in accordance with the average luminance level, and data indicative of the number of sustaining pulses for each of sub-fields which number determines a luminance in each of the cells, (e) a third circuit for selecting, based on the results and the total number of sustaining pulses, one of an amplitude of a first sustaining voltage dose to a voltage at which a luminance is saturated, and an amplitude of a certain period of second sustaining amplitude in which a luminance remains almost unchanged even if the sustaining voltage is increased, as an amplitude of a sustaining voltage in each of the sub-fields, and for transmitting an amplitude selection signal indicative of the thus selected amplitude, and (d) a fourth circuit for producing image data by which the plasma display panel is driven, based on the image data, in accordance with the amplitude selection signal, wherein an amplitude of the second sustaining voltage is selected as an amplitude of one of sustaining pulses to be applied to the scanning and sustaining electrodes in a sustaining period in at least one sub-field among the plurality of sub fields.
In yet another aspect of the present invention, there is provided a plasma display unit including a plasma display panel defined above, and a circuit for driving the plasma display panel, defined above.
The advantages obtained by the aforementioned present invention will be described hereinbelow.
In a plasma display panel in accordance with the present invention, a scanning electrode is designed to have partial cutout, and a sustaining electrode is designed to have partial cutout. A first trace electrode makes electrical contact with the scanning electrode, and a second trace electrode makes electrical contact with the sustaining electrode. A curve indicating a relation between a luminance and a sustaining voltage in a cell includes at least one intermediate region in which a luminance remains almost unchanged even if the sustaining voltage is increased. The sustaining pulses are designed to have an amplitude equal to the sustaining voltage. These structures make it possible to fabricate a plasma display panel in a smaller size, more readily and in smaller fabrication costs, display images at a gray scale equal to or greater than the number of sustaining pulses, and reduce power consumption with a high and uniform gray scale being maintained.
The above and other objects and advantageous features of the present invention will be made apparent from the following description made with reference to the accompanying drawings, in which like reference characters designate the same or similar parts throughout the drawings.